1. Technical Field
This invention applies to turbine engine rotor assemblies in general, and to apparatus for sealing between adjacent rotor blades and for damping the vibration within a turbine engine rotor assembly in particular.
2. Background Information
Turbine and compressor sections within an axial flow turbine engine generally include a rotor assembly comprising a rotating disc and a plurality of rotor blades circumferentially disposed around the disc. Each rotor blade includes a root, an airfoil, and a platform positioned in the transition area between the root and the airfoil. The roots of the blades are received in complementary shaped recesses within the disc. The platforms of the blades extend laterally outward and collectively form a flow path for the fluids passing through the turbine. A person of skill in the art will recognize that it is a distinct advantage to control the passage of fluid from one side of the platforms to the other side of the platforms via gaps between the platforms. To that end, it is known to place a seal between the blade platforms to control such fluid leakage.
During the operation of the turbine engine, the rotor assemblies rotate at a variety of speeds through fluids that vary in temperature, pressure, and density. As a result, the blades may be excited into vibrating relative to the disc. Unchecked vibrating rotor blades can negatively affect not only the performance of the engine, but also the allowable life of the components.
A person of skill in the art will recognize that it is known to provide means for damping the vibratory motion of rotor blades within a turbine engine rotor assembly. In some embodiments, the damping means also acts as the seal between the platforms. A possible disadvantage to this approach is that the optimum sealing material may not be an optimum damping material. Hence, the performance of either or both functions may be compromised. In other embodiments, the damping means and the seal means are independent of one another. The damping means is positioned to act against the root-side surface of the platform and the sealing means is slid in under the platforms, between the damping means and the platforms. A disadvantage of this approach is that often the seal must be installed blindly after adjacent blades are installed in the disc. Seals which are slid in blindly require guiding means, usually in the form of additional surfaces cast in the rotor blade. In sum, what is needed is a means for damping vibrations in a turbine engine rotor assembly and a means for sealing between adjacent rotor blades which overcomes the aforementioned disadvantages.